/**
 * 随机生成字符串
 * @param len 指定生成字符串长度
 */
export const getRanNum = function() {
  var result = []
  for (var i = 0; i < 4; i++) {
    var ranNum = Math.ceil(Math.random() * 25)
    result.push(String.fromCharCode(65 + ranNum))
  }
  return result.join('')
}

